Manifold imaging with thermal activator contained in a silica gel layer

ABSTRACT

A manifold imaging method and member is disclosed wherein the imaging layer is activated by a thermal activator which is incorporated in the member by means of a gel layer. By heating the imaging member the gel activates the imaging layer for use in the manifold imaging process.

Umted States Patent 1 1 1111 3,912,504

Kropac Oct. 14, 1975 MANIFOLD IMAGING WITH THERMAL [56] References Cited ACTIVATOR CONTAINED IN A SILICA GEL UNITED STATES PATENTS LAYER 3,303,043 2/1967 Halpaap et al 117/335 5 Inventor; Joseph M Kropac Williamson, 3,598,581 7 8/1971 Reinis 96/l.5

N.Y. I Primary ExaminerNorman G. Torchin [73] Ass1gnee: gel-ox Corporation, Stamford, Ass-mam Examiner lnuis Falasco onn.

[22] Filed: Jan. 21, 1974 [57] ABSTRACT [.21] APPL 435,381 A manifoldimaging method and member is disclosed wherein the imaging layer is activated by a thermal activator which is incorporated in the member by means [52] US. Cl;- 96/1 M; 96/1.3; 96/l.5 f a gel layer By heating the imaging Inember the gel [51] 603G 5/003 6036 13/24; 6036 5/04 activates the imaging layer for use in the manifold im- [58] Field of Search 96/1.5, 1.8, 1.3, 1 M; aging process l17/l7.5, 23 A 20 Claims, 2 Drawing Figures MANIFOLD IMAGING WITH THERMAL ACTIVATOR CONTAINED IN A SILICA GEL LAYER BACKGROUND OF THE INVENTION This invention relates to the manifold imaging process and more particularly to a novel imaging member and method.

There has recently been discovered an imaging technique generally referred to as the manifold imaging method wherein an imaging member comprising a donor layer, imaging layer and receiver layer is employed. The imaging layer is electrically photosensitive and in one form comprises an electrically photosensitive material such as metal-free phthalocyanine dispersed in an insulating binder. Typically, the imaging layer is coated on the donor layer and the coated substrate combined is termed a donor. When needed, in preparation for the imaging operation, the imaging layer is activated as by contacting it with a swelling agent, softening agent, solvent or partial solvent for the imaging layer. The imaging layer is typically exposed to an imagewise pattern of light to which it is sensitive and while sandwiched between the donor and receiver layers and subjected to an electric field the imaging layer fractures upon the separation of the donor and receiver layers providing complementary positive and negative images on the donor and receiver layers in accordance with the image to which it was exposed.

Such manifold imaging method is more fully disclosed in US. Pat. No. 3,707,368 to Van Dorn which patent is hereby incorporated by reference. As is taught in said patent the imaging layer is typically activated by applying thereto an activator material. Subsequent efforts in the manifold imaging science has produced other methods of activation such as therrno-activation as disclosed in US. Pat. No. 3,598,581 to Reinis which patent is hereby incorporated by reference. Although thermo-activation as disclosed by Reinis eliminates the need for handling liquid activators at the imaging site, such process provides a wax component on the final image and a carryover in image background areas. There is desired a thermo-solvent activator method which reduces the amount of wax on the image and background areas.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an improved manifold imaging method.

Another object of this invention is to provide a novel imaging member useful in the manifold imaging process.

Another object of this invention is to provide a method for conveniently and accurately applying an activator to an imaging layer in the manifold imaging method.

In accordance with this invention there is provided a manifold imaging member and method whereby a thermo-activator or thermo-solvent for the imaging layer is incorporated into the imaging member by means of a gel layer which activates the imaging layer at the appropriate time by applying heat to the imaging member. Thus the imaging member of this invention incorporates, in addition to the donor, receiver and imaging layer, a fourth layer which carries the activator in the form of a gel. The activator activates the imaging layer so as to render the imaging layer structurally fracturable in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which the imaging layer is sensitive.

The gel is prepared in accordance with this invention by simply combining finely divided hydrophobic silica with the thermo-solvent. The proportion depends upon the nature of the thermo-solvent and the particular silica employed. In most instances a suitable gel is formed by adding to the activator about 5 percent to about 20 percent silica by weight. Typically, suitable gels are formed by combining silica and activator in a wide range concentration depending upon the rigidity desired in the gel. Usually amounts of silica up to about 30 percent provide acceptable gels. Preferably the gel is nearly rigid and flows slowly when the wax is melted. The misture is solid at normal room temeratures. Any suitable thermo-solvent activator which forms a gel by the addition of hydrophobic silica can be employed. Typical prior art thermo-activators or solvents include those known in the prior art. The term thermoactivator or thermosolvent is intended to mean herein those materials which have a melting point lower than the imaging layer and which, upon melting, become an activator for the imaging layer. That is, the material structurally weakens or reduces the cohesive strength of the imaging layer such that the layer fractures in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which the layer is sensitive. In such weakened condition the layer cleaves or fractures in accordance with the imagewise exposure when the donor and receiver layers are separated. Particularly preferred thermoactivators are those which are solid at or slightly above room temperature but which melt below F. Such thermo-activators include long chain petroleum waxes with from about 16 to about 37 carbon atoms in the chain. Typical waxes include hexadecane, heptadecane, octadecane, nonadecane eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, octacosane, triacentane, dotriacontane, tetratriacontane, hexatriacontane, and octatriacontane and mixtures thereof. Other thermo-activators known in the art include m-terphenyl, Aroclors (chlorinated polyphenyls available from Monsanto Co., St. Louis, Mo.), biphenyl, polybutenes and mixtures thereof.

Any suitable hydrophobic finely divided silica can be employed, such silica is commercially available under various tradenames and generally have a particle size in the range of from about 10 to about 30 millimicrons. Examples of such silicas are Silanox 101 and Organo- Sil available from the Cabot Chemical Company, Boston, Massachusetts and Aerosil R-972 available from Degussa Inc., New York, New York. Other similar get forming silica products can be employed in accordance with this invention. Hydrophobic silica is a specially prepared product from silicon dioxide, a more complete description is found in US. Pat. No. 3,720,617 to Chaterji et al, which patent is hereby incorporated by reference.

The gel layer is incorporated into the imaging member in any suitable location. The gel layer can be hot melt coated onto a warm imaging layer before the member is formed. The imaging layer is preferably warmed to the melting point of the thermo-activator. Coating the activator of this invention can also be accomplished on the receiver layer. When coating on a layer which has not been warmed the gel is usually heated to a higher temperature. Typically the gel layer is provided by first mixing the thermo-activator in its melted, liquid state with an appropriate amount of silica as indicated above. The silica is added to the activator preferably with constant stirring. In a preferred method of preparing the thermo-activator layer, the melted activator/silica mixture is precipitated in an alcohol. Typical alcohols include ethanal, isopropanol, methanol, and other low molecular weight alcohols. The alcohol is preferably anhydrous. The precipitate is usually milled to provide a dispersion in the alcohol then coated from the dispersion onto either donor layer, imaging layer or receiver layer. The coating is heated to drive off the alcohol. In most instances, heated rollers are employed to receive the donor and receiver layers in web form which carry the imaging and gel layers. Upon heating the member the thermoactivator activates the imaging layer.

In another embodiment the gel is applied at the imaging site. Typically such application is by means of a soft bristle brush, extruder or any other commonly known coating mechanism for applying a gel to a surface. As taught in the prior art, the activator can be employed either before or after, the image exposure step of the imaging process.

In general, the manifold imaging member of the prior art employing thermo-activated imaging layers are also useful in the member and process of this invention. Thus, typical thermoplastic, metal and paper donor and receiver layers of the prior art are also useful herein. In addition, the typical thermo-activated electrically photosensitive imaging layers of the prior art are employed herein. Numerous exemplary materials useful in preparing the donor, receiver and imaging layers are listed in the above-mentioned U.S. Pat. No. 3,598,581.

Here, as in the prior art, the thermo-activator to be employed is chosen so as to effect the desired activation of the imaging layer keeping in mind the electrically photosensitive materials and binders employed therein.

An advantage provided by the instant invention is the control over wax carryover onto the lamps background areas. That is, in the prior art thermo-activation as represented by Reinis provides about a 60/40 percent split of the thermo-activator layer. In accordance with this invention, the amount of the wax left on the complementary images is concentrated on one image while the other image has relatively less wax. The imaging system is thus operated so as to take advantage of the control over wax carryover. Wax carryover is further controlled by the addition of small amounts of microcrystalline wax to the thermo-activator. Amounts up to about 4percent by weight of the thermo-activator provide images wherein most of the wax is left on one image thus reducing the amount of wax on the other image. Normally wax reduction by such common means as extruder, devices normally employed for extruding gels or knife edge devices for dispersions. By controlling the amount of activator in the gel and the amount of the gel incorporated in the imaging member of this invention, a high degree of control is exercised over the amount of activator finally applied to the imaging layer during the imaging process.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention will be more clearly understood, reference is now made to the accompanying drawings in which an embodiment of the invention is illustrated by way of example.

FIG. 1 is a side sectional view ofa photosensitive imaging member of this invention.

FIG. 2 is a side sectional view diagrammatically illustrating the process steps of this invention.

Referring now to FIG. 1, imaging layer 2 comprising photosensitive particles 4 dispersed in binder 3, is deposited on an insulating donor substrate sheet 5. The image receiving portion of the manifold set comprises receiver layer 6. In this embodiment gel layer 7 is incorporated between imaging layer 2 and receiver layer 6. In the usual case either or both of layers 5 and 6 are transparent to electromagnetic radiation to which the imaging layer is sensitive and conveniently has electrically conductive outer surfaces.

Referring now to FIG. 2, the first step illustrated in the imaging process is the activation step. In this stage of the imaging process the manifold set comprising electrically insulating donor layer 17, imaging layer 12, electrically insulating receiver layer 16 and gel layer 19 is passed between heating rollers 26 which heat the member thus activating imaging layer 12. The activator serves to swell or otherwise weaken and thereby lower the cohesive strength of the imaging layer 12. Once the I proper physical properties have been imparted to imaging layer 12, the manifold set proceeds through electrodes l8 and 21 which are connected to potential source 28 through resistor 30. Electrodes 18 and 28 can take any suitable form for imparting an electrostatic charge to the layers. One convenient form is a pair of conductive rollers.

The manifold set is then advanced to imaging station 27 where it is exposed to light image 29. Light image 29 may be light projected through a transparency or light information projected from an opaque subject. In a continuous operation the light image preferably is projected through a slit so that there is little or no relative motion between the projected image and the manifold set during exposure. Although not shown, other sequences of method steps can occur. For example, a suitably charged imaging layer can be exposed to appropriate radiation before the sandwich is formed. Such a process is fully described in U.S. Pat. No. 3,615,393 hereby incorporated by reference.

Subsequent to imaging, receiver layer 16 is separated from donor layer 17 over roller 32 thus fracturing the imaging layer in accordance with the light image to which it was exposed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following Examples further specifically illustrate various embodiments of the improved imaging member and method. The parts and percentages are by weight unless otherwise indicated.

EXAMPLE I A black color imaging layer is prepared by first providing the x-form metal-free phthalocyanine as described in Example I of the aforementioned U.S. Pat. No. 3,707,368. About 2.5 grams of the x-form phthalocyanine is added to about 1.2 grams of Algol Yellow GC, l,2,5,6-di- (C,C'-diphenyl) thiazoleanthraquinone, C. I. No. 67300, available from GAF and about 2.8 grams of purified Irgazine 2' BLT available from Geigy Chemical Co. The mixture is milled in-a ball mill I with 60 ml. of DC Naphtha 2032 for 4 hours.

A binder is prepared by first dissolving 3 parts of Polyethylene DYLT, 1.5 parts of Paraflint RG, 0.5 parts of Elvax 420 and 2.5 parts of Piccotex 75 in 20 ml. of Sohio Odorless Solvent 3440 by heating the mixture with stirring. The solution is allowed to cool and the resulting paste is added to the milled pigment. The pigment/paste mixture is ball milled for about 16 hours. The milled paste is then placed in a polyethane jar which is heated in a water bath in a temperature of 65C for about 2 hours. The paste is then allowed to cool and slurried in about 70 parts of 2-proxanol. The paste-like mixture is then coated on 1 mil Mylar a polyester formed by the condensation reaction between ethylene glycol and tetphtalic acid available from E. I. DuPont de Nemours & Co. Inc.) with a No. 22 wire wound drawdown rod to produce a coating thickness when dried of approximately 8 to 10 microns. The coating and one mil Mylar sheet is then dried in the dark at a temperature of about 43C. for 5 minutes.

A gel is then prepared by combining 1.5 parts of a hydrophobic silica, Aerosil R-972 with 18 parts of melted paraffin wax with constant mixing. The mixture is precipitated in 100ml. of alcohol, allowed to cool to room temp., then ball milled to form a dispersion in the alcohol. The dispersion is then coated over the above prepared imaging layer by means of a No. 36 wire wound drawdown rod and dried for 5 minutes at 65C. in a forced-air oven. A 1 mil Mylar receiver is placed on a grounded electrode heated to 54C. The donor, with imaging layer towards the receiver is placed on the heated receiver. The activator melts and the sandwich is charged by passing a 9KV corona discharge device over it. After charging the imaging layer is exposed to an imagewise pattern of incandescent light at a total energy of 0.55 foot candle seconds. While heated, the donor and receiver layers are separated providing a positive image of the original on the donor layer and a negative image on the receiver.

EXAMPLE II The procedure of Example I is repeated except 3 percent by weightof the paraffin wax of microcystalline wax (Paraflint RC) is added to the wax/silica mixture while melted. Similar results of image formation are obtained.

EXAMPLES III & IV

The procedures of Examples I and II are repeated except that there is no imagewise exposure of the imaging layer. The amount of thermo-activator on the receiver layer is determined in each case. Without microcystalline wax (Example III) the amount of thermo-activator on the receiver is about 40 percent by weight of that added to the imaging member. With microcystalline wax (Example IV) the amount of thermoactivator on the receiver layer is about 25 percent by weight of the amount added to the imaging member.

EXAMPLES V & VI

The procedures of Examples III are repeated except the coated imaging layer is dried at 75C. The amount of activator on the receiver layer without microcystalline wax (Example V) is about 31 percent by weight of the amount of activator added to the imaging member. The amount of activator containing microcystalline wax remaining on the receiver layer (Example VI) is about 20 percent of the amoun'tof thermo -acti'vator added'to the imaging member.

Although specific components and proportions have been stated in the above description of preferred embodiments of the invention, other typical materials as listed above if suitable may be used with similar results. In addition, other materials may be added to the mixture to synergize, enhance or otherwise modify the 0 properties of the imaging layer. For example, various surface dopants on the photoconductive layer can enhance photoinjection capability. However, other dopants can interfere or prevent such photoinjection.

What is claimed is:

1. In a manifold imaging member comprising a donor layer, receiver layer, an electrically photosensitive imaging layer and a thermo-activator layer, the improvement wherein said thermo-activator layer is a gel comprising a mixture of finely divided hydrophobic silica and a thermoactivator.

2. An imaging member of claim 1 wherein at least one of said donor and receiver layers is transparent.

3. The imaging layer of claim 1 wherein siad thermoactivator contains a microcrystalline wax.

4. The imaging member of claim 1 wherein the silica gel contains finely divided silica having a particle size in the range of from about l0 millimicrons to about 30 millimicrons.

5. The imaging member of claim 4 wherein said gel layer contains a thermo-solvent activator for said imaging layer.

6. The imaging member of claim 4 wherein said gel layer is coated on said imaging layer.

7. An imaging member of claim 4 wherein said gel layer is coated on said receiver layer.

8. In a manifold imaging member comprising a donor layer, a thermo-activator layer on said donor layer, an electrically photosensitive layer residing on said thermoactivator layer and a receiver layer over said imaging layer, the improvement wherein said thermoactivator layer is in the form of a gel comprising a mixture of finely divided hydrophobic silica and a thermoactivator.

9. An imaging layer of claim 8 wherein said imaging layer comprises an electrically photosensitive material dispersed in a binder.

10. An imaging member of claim 1 wherein said im aging layer comprises an electrically photosensitive material dispersed in a binder.

11. An imaging member of claim 1 wherein said imaging layer is of a black color.

12. An imaging member of claim 8 wherein said imaging layer is of a black color.

13. An imaging member of claim 8 wherein said gel layer contains a microcrystalline wax.

14. An imaging process which comprises the steps of:

1 providing an imaging member of claim 1;

2 heating said imaging member whereby said activator layer melts and renders said imaging layer structurally fracturable in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which said imaging layer is sensitive;

3 subjecting said imaging layer to an electrical field and exposing said imaging layer to electromagnetic radiation to which it is sensitive; and,

LII

4 separating said donor and receiver layers while said member is subjected to said electrical field whereby said imaging layer fractures in imagewise configuration providing a positive image on one of said donor and receiver layers and a negative image on the other.

15. The process of claim 14 wherein said gel thermo activator layer resides between said imaging layer and said receiver layer.

16. The method of claim 14 wherein said heat is applied by means of a pair of heating rollers.

17. The method of claim 14 wherein at least one of said donor and receiver layers is at least'partially transactivator layer is coated on said receiver layer. 

1. IN A MANIFOLD IMAGING MEMBER COMPRISING A DONOR LAYER, RECEIVER LAYER, AN ELECTRICALLY PHOTOSENSITIVE IMAGINING LAYER AND A THERMO-ACTIVATOR LAYER, THE IMPROVEMENT WHEREIN SAID THERMO-ACTIVATOR LAYER IS A GEL COMPRISING A MIXTURE OF FINELY DIVIDED HYDROPHOBIC SILICA AND A THERMOACTIVATOR.
 2. An imaging member of claim 1 wherein at least one of said donor and receiver layers is transparent.
 3. The imaging layer of claim 1 wherein siad thermoactivator contains a microcrystalline wax.
 4. The imaging member of claim 1 wherein the silica gel contains finely divided silica having a particle size in the range of from about 10 millimicrons to about 30 millimicrons.
 5. The imaging member of claim 4 wherein said gel layer contains a thermo-solvent activator for said imaging layer.
 6. The imaging member of claim 4 wherein said gel layer is coated on said imaging layer.
 7. An imaging member of claim 4 wherein said gel layer is coated on said receiver layer.
 8. In a manifold imaging member comprising a donor layer, a thermo-activator layer on said donor layer, an electrically photosensitive layer residing on said thermoactivator layer and a receiver layer over said imaging layer, the improvement wherein said thermo-activator layer is in the form of a gel comprising a mixture of finely divided hydrophobic silica and a thermo-activator.
 9. An imaging layer of claim 8 wherein said imaging layer comprises an electrically photosensitive Material dispersed in a binder.
 10. An imaging member of claim 1 wherein said imaging layer comprises an electrically photosensitive material dispersed in a binder.
 11. An imaging member of claim 1 wherein said imaging layer is of a black color.
 12. An imaging member of claim 8 wherein said imaging layer is of a black color.
 13. An imaging member of claim 8 wherein said gel layer contains a microcrystalline wax.
 14. An imaging process which comprises the steps of: 1 providing an imaging member of claim 1; 2 heating said imaging member whereby said activator layer melts and renders said imaging layer structurally fracturable in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which said imaging layer is sensitive; 3 subjecting said imaging layer to an electrical field and exposing said imaging layer to electromagnetic radiation to which it is sensitive; and, 4 separating said donor and receiver layers while said member is subjected to said electrical field whereby said imaging layer fractures in imagewise configuration providing a positive image on one of said donor and receiver layers and a negative image on the other.
 15. The process of claim 14 wherein said gel thermo activator layer resides between said imaging layer and said receiver layer.
 16. The method of claim 14 wherein said heat is applied by means of a pair of heating rollers.
 17. The method of claim 14 wherein at least one of said donor and receiver layers is at least partially transparent to electromagnetic radiation to which said imaging layer is sensitive and said exposure is through said layer.
 18. The method of claim 14 wherein said gel thermo-activator layer comprises up to about 30 percent by weight hydrophobic submicroscopic silica.
 19. The imaging method of claim 14 wherein said imaging layer is coated on said donor layer and said gel thermo activator layer activator layer is coated on said imaging layer.
 20. The imaging process of claim 14 wherein said gel activator layer is coated on said receiver layer. 